Photographic shutter



Sept.- 5, 1944. T. H. JOHNSON PHCTOGRAPHIC SHUTTER "Filed Oct. 24, 19423 Sheets-Sheet 1 p 1944. T. H. JOHNSON 2,357,331

PHOTOGRAPHIG SHUTTER Filed Oct. 24, 1942 3 Sheets-Sheet 2 THOMAS 166 2/0NSOA/ 64.4 46.4..

Sept. 5, 1944. 'r. H. JOHNSON PHOTOGRAPHIC SHUTTER Filed 001;. 24, 19423 Sheets-Sheet 3 a, ii

HMS ON rroanvgl;

Patented Sept. 5, 1944 UNITED STATES PATENT OFFICE rnorocaarmo SHUTTERThomas H. Johnson, Swarthmore, Pa.

Application October 24, 1942, Serial 463,196

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700, G. 757) 8 Claims.

tached either in front of or behind the lens of can'be photographed withthe full available aperture of the camera without introducing reducingfilters.

An essential feature of the subject shutter which enables it to achievethe above result is that the louvres or shutter vanes, which define theexposure time, are in continuous and rapid motion and are not requiredtobe either accelerated or decelerated during the time of the exposure.Since this continuous motion of the louvres results in a series ofexposures, a synchronizing device is provided which allows only one ofthe series of louvre shutter exposures to coincide with the opening ofthe between-the-lens shutter.

Other objects and advantages of the invention will be apparent from thefollowing detailed description thereof.

Referring to the accompanying drawings in which is illustrated oneembodiment of the inven-' on line 3-3 of Figure 2 also showing theposition of the shutter with reference to the camera;

Figure 4 is a section on line '4--4 of Figure 2; Figure 5 15a section online 55 of Figure 2 showing the arrangement of brushes and rotor of thecircuit-interrupter for synchronizing the triggering current for themain between-the-lens ing louvres showing the angular range of theposition of the louvres for which rays parallel to the optical axis ofthe camera pass through the shutter.

I, In the form herein disclosed the shutter comj prises five verticalsets of louvres or shutter vanes I mounted for rotation in a rectangularframe composed of vertical side members 2 and 3 and horizontal top andbottom members 4 and S Each set consists of live laterally spaced andparallel vanes or louvres whose ends are secured in disks 6 and 1. Disk6 secures the lower ends of the louvres and is supported within theframe by a depending stub shaft 8 joumaled in a ball bearing 9; thelatter-being mounted in the bottom bearing-support member Ill of theframe. Disk I secures the upper ends of the louvres and has-an'upwardlyextending stub shaft H journaled in ball bearings l2 and 13, the formerbeing mounted in the top' frame member 4 and the latter in the topbearing-support member i4 of the frame. Shaft II is longer than shaft 1and has a gear l5 connected thereto within the clearance providedbetween the frame members 4 and I4. The gears l5 of the various setsmesh with one another and in order that the louvres I shall be free torotate without interference between the sets, the gears and theircorresponding sets of louvres are mounted with their axes along twoseparate lines as shown in Figure 3.

The several sets of louvres are simultaneously rotated by ashutter-driving mechanism including a motor l6 having a driving shaft I!provided with a worm l8. Worm l8 meshes with a worm gear I! fixed onshaft 20, the latter being an integral extension of the shaft ll of themiddle set of louvres and projecting upwardly'beyond the coupled by aclutch connection 28.

shutter 01' the camera with the phase of rotation of the louvres;

Figure 6 is a circuit diagram showing the connections of thesynchronizing circuit,-and

Figure 7 is a section of one of the sets of rotattop of the frame asshown in Figure 2. Gear is is housed within a gear box 2| which issupported in fixed, outwardly spaced, relation to the top of the shutterframe upon the top flange of the circuit-interrupter housing 22; thebottom flange of the housing resting upon and being fixed to the topmember 4 of the frame. Upon the top face of the gear box 2| is fixedlymounted 'an inverted cup-shaped fitting 23 into which the end of shaft20 extends and wherein the radial loads are taken by an annular ballbearing 24. Connected to the fitting 23 by a screw-threaded joint 25 isthe casing of a magnetic tachometer 28. The shaft 21 of thetachometer-is driven by the shaft 20 of the shutter driving mechanism towhich it is netic tachometer may be any suitable and well known type andits specific construction forms no part of the present invention. Theangular velocity of the sets of louvres is dependent upon the speed ofrotation of the electric motor and this is controlled by a rheostat 28and indicated by the tachometer 26. The rheostat and the mo- .tor aredisposed adjacent a common side of the The 'magpositions of the louvresat which light passes through to the lens of the camera in a directionparallel to the optical axis. As is apparent from the construction shownin Figures 1 and 7, the parallel vanes or louvres of each set arerigidly mounted together and capabl of rotation as a unit so that therange of angles, in a. complete rotation of the unit, for which rays oflight are allowed to pass through the shutter is small compared with thecomplete rotation. The central louvre of each set is broader than theothers and when the louvres are perpendicular to the optical axis thesebroader louvres overlap so that no light is allowed to pass between thesuccessive sets. The spacing between the louvres of each set is suchthat the diffraction pattern from each slit determined by two adjacentlouvres is not so broad as to effect the definition of the lens. Thisconsideration is determined by well-known principles of physical optics.The louvres l are specially treated with a blackening coat to preventspecular reflection from their surfaces which would cause bright objectsto cast a streak of light across the camera film perpendicular to theaxis of rotation of the louvres.

The position of the louvre shutter with reference to the aerial camerais graphically shown in Figure 3. The cone 33 of the camera and one ofthe lens elements 34 thereof are represented by dotted lineconstruction. In order to avoid transmitting vibrations from the louvresto the camera, the shutter is attached to the camera by springs 35. Eachspring is secured at one end to an anchoring bolt or stud 35 fixed tothe shutter-mounting plate 31 and at its opposite end to a bracket 38(Figure 1) attached to a suitable part ofthe camera structure. Themounting plate bridges the cone of the camera. Between the mountingplate and the cone is a layer 33 of sponge rubber. The shutter ismounted on the plate 31 by means of the cover 4 plate 40 attached to therear of the shutter frame. The rear cover plate also serves to excludedirt and other foreign matter from mechanical parts of the shutter and asimilar function is performed by the front cover plate 4|. A thin coverplate 42 is fastened to the top frame member 4 for exeluding foreignmatter from the bearings I2 and I3.

The representation of the camera in Figure 3 includes a conventionalshowing of only a part of an electrically triggered between-the-lensshutter mechanism in which the shutter leaves in part S. are operated bya. triggering solenoid 44 coacting with the shutter-actuating member M.The construction and operation of this type of shutter is well known inthe art and forms no part of the subject invention except insofar ascombined and synchronized with the louvre shutter to allow only one ofeach series of louver shutter exposures to coincide with the opening ofthe between-the-lens shutter. However, the solehold 44 and otherelements of the shutter operating circuit pertinent to the subjectinvention, such as the switch 43 and the relay 3|, are shown in thecircuit diagram of Figure 6. The switch 43 control the operation of therelay 3| through a main circuit which includes the battery 45,

switch 43, relay winding W, and conductors 46,

circuit through which current is conducted to the triggering solenoid44. This circuit includes the battery 45, triggering solenoid 44 whichoperates the shutter-actuating member M of the betweenthe-lens shutterof the camera, switch 52 and conductors 53 connected to the batteryleads 46 and 48. One of the contact elements of the switch 52 is carriedby the relay armature which is tensioned to close the switch when notattracted to the relay core.

As shown in Figure 2, the rotor is fixed on the shutter drive shaft 20and is encased within the housing 22. As shown more particularly inFigure 5, the brushes 49 and 5| extend into the housing 22 throughopenings in the side wall thereof and contact the rotor radially of theperipheral face of the latter. Embedded in the rotor is an insulatedsegment 54 having exposed end portions flush with the peripheral face ofthe rotor at diametrically opposite locations. These end portions areadapted to be contacted by the brush 5| during the rotation of the rotor50 for periodically breaking the parallel circuit and interrupting thefiowof current to the relay 3|. As shown in Figure 2 of the drawings,the rotor 50 has conducting flanges extending on each side of theinsulating insert 54 to the circumference of the rotor. The brush 49 isoilset with respect to the rotor 50 and brush 5| in such way that itcontacts one of these flanges to make continuous contact with theconducting part of the rotor. Brush 49 is carried by a holder 55 havinga direct and fixed connection with the interrupter housing 22.

' Brush 5| is carried by a holder 56 fixedly mounted eration of therelay 3|, and hence the triggering lowing the passage of light .raysfrom the object to the camera lens. The time of the opening of thelouvres is indicated by the magnetic tachometer 26 and may be regulatedby the rheostat 29. No exposure of the film occurs, however, until andunless the between-the-lens shutter of the camera is opened by operationof the shutter-tripping solenoid 44 insynchronization with the phase ofrotation of the louvres. Normally, the switch" of the main relay-controlcircuit is closed and the relay .3! is thereby operated to open theswitch 52 of the secondary circuit. Hence, the shuttertripping solenoidremains inactive so long as the switch 43 is closed. When an exposure ofthe film is desired, the switch 43 is opened to release the relay fromthe control of the main circuit and to subject it entirely to thecontrol of the current in the parallel circuit passing through the rotor50 and the brushes 49 and 5|. This transfer of control of the relay fromthe main circuit to the parallel circuit is accomplished withoutimmediately effecting the operation of the relay. However, when theparallel circuit is broken by the rotation of the rotor.50 to a positionwhere the brush 5| is engaged with the insulated segment 54 the relay isdeenergized and the switch 52 automatically closesv the secondarycircuit through which the shutter-tripping solenoid 44 is operated.

Although the contact made by brush 5| with the rotor 50 is broken bysegment 54 for a very short period of time, the break is, in general,suflicient to allow the relay to release the armature. Operation of therelay to reset the shutter-tripping solenoid, after each shuttertripping action of the latter, is accomplished through the main relaycontrol circuit by closing switch 43 since the resistance R, Figure 61is of such a value that the current through the parallel circuit isinsufficient to reenergize the relay. Hence, the switch relayoperatedswitch 52 remains closed after the initial break in the parallelcircuit, for a period of time, controlled by the switch 43, of uiiicientduration to allow the current in the secondary circuit to build up andcaus the triggering solenoid to operate the between-the-lens shutter.The combination and synchronization of the high speed louvre shutter andthe between-the-lens shutter results in a shorter time of exposure ofthe camera film than is obtainable with the between-the-lens shutteralone.

It is understood that the invention i not limited to the constructionherein specifically illustrated and described but can be embodied inother forms, withinlthe scope of the appended claims, without departurefrom the general principle thereof.

I claim: 4

1. A photographic shutter comprising a frame, multiple sets of laterallyspaced parallel louvres mounted in the frame, each set being rotatableabout an individual axis and the louvres of each set being rigidlymounted together for rotation as a unit about the axi of the set, andmeans for rotating the said sets simultaneously about their 3. Aphotographic shutter comprising multiple sets of parallel and laterallyspaced louvres, said sets being connected together for simultaneousrotation about their respective axes and thelouvres of each set beingrigidly mounted together and capable of rotation as a unit so that in acomplete rotation of the unit the range of angles for which rays oflight are permitted to pass through the shutter is small compared withthe complete rotation.

4. A photographic shutter comprising a frame, staggered sets oflaterally spaced parallel louvres rotatably mounted in the frame andhaving synchronous exposure periods, each set being rotatable about anindividual axis and the louvres of each set being rigidly mountedtogether for rotation as a unit about the axis of the set, the centrallouvre of each set being broader than the others of the set so that whenthe position of the louvres is perpendicular to the optical axis thecentral louvres overlap and prevent the passage of light betweenadjacent sets.

5. A shutter for attachment to a camera including a frame, louvresrotatably mounted in the frame and connected together to be movedsimultaneously to open and close the aperture of the frame, a mountingplate on the back of the said frame and adapted to bridge the cone ofthe camera, elastic elements secured to the said plate and extendableinto the said cone for attachment to a structural part of the camera forholding the plate against the cone of the camera.

6. A shutter for attachment to a camera including a frame, louvresjournaled in the frame and connected together to be rotatedsimultaneously to open and close the aperture of the frame, a mountingmember on the back of the frame and adapted to bridge the cone of thecamera, tension elements secured to the mounting member and attachableto a structural part of the camera for holding the member under tensionagainst the said cone of the camera, and an elastic body secured to themember to engage the cone and provide a resilient pad between the coneand the mounting member in the attached position of the shutter.

7. In a camera, the combination of a main shutter of between-lens type,an additional shutter of rotatable louvres optically aligned with themain shutter, operating mechanism associated with the additional shutterand operable for rapidly rotating the louvres simultaneously to open andclose said shutter at a given frequency for a. definite time period,operating mechanism associated with the main shutter and operable foropening the said shutter at less frequency than the louvre shutterduring the said. given time period, and a shutter synchronizingmechanism interconnecting the respective shutter-operating mechanismsand operated thereby for causing the coincidences of the shutteropenings to occur along the optic axis of the camera.

8. In a camera, the combination of a betweenthe-lens shutter having ashutter-actuating member, a rotatable louvre shutter, means for rotatingthe louvre shutter, an electrical means for synchronizing the operationof the two shutters com prising a triggering solenoid connected to theshutter-actuating member, a relay for controlling the current to thesolenoid, a rotor driven by the louvre-shutter rotating means andelectrically connected to one side of the relay, an insulating segmenton said rotor, an adjustable brush electrically connected to the otherside of the relay and engaged with the rotor to be contacted atintervals by the insulating segment to open the circuit through therelay, said brush being adjustable on the-rotor to vary the timedrelation between th louvre shutter and the between-the-

